A first example of an imaging arrangement for use in this type of display is a barrier, for example with slits that are sized and positioned in relation to the underlying pixels of the display. In a two-view design, the viewer is able to perceive a 3D image if his/her head is at a fixed position. The barrier is positioned in front of the display panel and is designed so that light from the odd and even pixel columns is directed towards the left and right eye of the viewer, respectively.
A drawback of this type of two-view display design is that the viewer has to be at a fixed position, and can only move approximately 3 cm to the left or right. In a more preferred embodiment there are not two sub-pixel columns beneath each slit, but several. In this way, the viewer is allowed to move to the left and right and perceive a stereo image in his/her eyes all the time.
The barrier arrangement is simple to produce but is not light efficient. A preferred alternative is therefore to use a lens arrangement as the imaging arrangement. For example, an array of elongate lenticular elements can be provided extending parallel to one another and overlying the display pixel array, and the display pixels are observed through these lenticular elements.
The lenticular elements are provided as a sheet of elements, each of which comprises an elongate semi-cylindrical lens element. The lenticular elements extend in the column direction of the display panel, with each lenticular element overlying a respective group of two or more adjacent columns of display pixels.
In an arrangement in which, for example, each lenticule is associated with two columns of display pixels, the display pixels in each column provide a vertical slice of a respective two dimensional sub-image. The lenticular sheet directs these two slices and corresponding slices from the display pixel columns associated with the other lenticules, to the left and right eyes of a user positioned in front of the sheet, so that the user observes a single stereoscopic image. The sheet of lenticular elements thus provides a light output directing function.
In other arrangements, each lenticule is associated with a group of four or more adjacent display pixels in the row direction. Corresponding columns of display pixels in each group are arranged appropriately to provide a vertical slice from a respective two dimensional sub-image. As a user's head is moved from left to right, a series of successive, different, stereoscopic views are perceived creating, for example, a look-around impression.
Known autostereoscopic displays use liquid crystal displays to generate the image.
When developing an LCD based auto-stereoscopic display, a compromise is made when designing the lenticular lens as to which sub-pixels under the lens are in focus and which are not. Only a subset of the pixels can be in focus and the remainder are slightly de-focussed. This problem is inherent to an LCD as the liquid crystal layer is typically only 3-4 microns thick and is physically confined by two flat glass plates. The LCD is a light shutter and therefore does not change the focussing, and the light sources for the lens are always situated in a single plane.
There is increasing interest in the use of organic light emitting diode (OLED) displays generally, as these do not need polarizers, and potentially they should be able to offer increased efficiency since the pixels are turned off when not used to display an image, compared to LCD panels which use a continuously illuminated backlight. Traditional OLED displays also have all pixels in a single plane, so that the problem of poor focus is also present in such displays.
This invention is based on the use of an OLED or other thin film emissive display such as an electroluminescent display within an autostereoscopic display system, and makes use of the additional design flexibility offered by these displays, in order to address the problem of out of focus pixels beneath the lenses of an autostereoscopic display.